mine is very similar to what you describe, though i have 141k on original block. i checked my vacuum and it's 6" Hg at all rpms with very little needle movement during revving. i think this means i have a wicked vac leak somewhere, probably the vac lines that are missing in several places. check your vac with a gauge and see if it's about right, plus you can diagnose a clogged cat with this method too. it's possible that you just forgot to hook up something like the brake booster that's just sucking in air like a mofohere's a page that will help you out, but you need to get a mityvac or some other vac gauge to use it.